Conventionally, to prevent seepage of liquid or gas between two opposing faces in various machines and apparatuses or other structures, a gasket is set between the two opposing faces.
For example, an antenna to aid communication between aircrafts and distant places is set on the outer surface of the body wall (outer board) of the aircrafts. Many of such antennas have a plate-like fixing board having an electric connector protruding from one surface thereof. The surface of the fixing board having the protruding electric connector is superposed on the outer face of the outer board, the connector is inserted into the inside of an aircraft from the hole formed on the outer board of the aircraft, and connected to an appropriate electric circuit in the aircraft. In this case, the fixing board of the antenna is generally installed removably with a bold on the outer board of the aircraft, where a gasket is set between the outer face of the outer board and the inner face of the antenna fixing board to seal the antenna fixing board.
To be specific, a bold hole is formed at the corresponding positions of the antenna fixing board and the outer board of an aircraft, a gasket having a through-hole formed at a position corresponding to the bold hole in the antenna fixing board and the outer board of the aircraft is placed between them, a bold is inserted from the outside of the antenna fixing board into the through-hole of the antenna fixing board, the gasket and the outer board of the aircraft, and a blind nut is set on the inner face of the outer board of the aircraft, whereby the antenna is fixed. In so doing, the gasket is compressed by the deformation of the fixing board due to bolding, which in turn provides a seal of the bold and the bold pore, as well as the outer board of the aircraft and the fixing board. Consequently, penetration of moisture into the aircraft can be prevented.
As a gasket used for sealing such an antenna fixing member on the outer board of an aircraft, for example, US2004/0070156A1 proposes a gasket material wherein an adhesive layer of a flexible polyurethane gel is formed on both the front and the back of a carrier sheet (substrate film). This publication describes that a gasket having an adhesive layer of a polyurethane gel maintains superior sealing property, since polyurethane gel is superior in the flexibility, elasticity, conpressibility, flexibility and the like, and nonreactive with the constituent materials (specifically aluminum etc.) of the outer board of aircrafts and antenna fixing board, and water (including brine).
There are many structures comprising two members with each surface facing the other surface (that is, forming a matching face of the two opposing faces), which are fixed not only at the fixing part of function articles on the above-mentioned outer board of an aircraft but also inside the aircraft.
In general, aircraft members are required to have high flame retardancy. Therefore, gasket is also requested to have high flame retardancy, and contains a halogenated flame retardant showing high flame retardancy. Although a gasket containing a halogenated flame retardant shows high flame retardancy, it produces a large amount of toxic halogen gas during molding processing and combustion to possibly corrode instruments and adversely influence human body and environment. Therefore, a gasket showing high flame retardancy, which does not generate toxic halogen gas during combustion, has been demanded. Moreover, since many of the members to be closely adhered to the gasket are metal plates, the gasket is required to have properties that do not discolor or corrode metal plates.